The StandardAutoloader

Overview

Zend\Loader\StandardAutoloader is designed as a PSR-0-compliant autoloader. It assumes a 1:1 mapping of the namespace+classname to the filesystem, wherein namespace separators and underscores are translated to directory separators. A simple statement that illustrates how resolution works is as follows:

$filename = str_replace(array('_', '\\'), DIRECTORY_SEPARATOR, $classname)
          . '.php';

Previous incarnations of PSR-0-compliant autoloaders in Zend Framework have relied upon the include_path for file lookups. This has led to a number of issues:

• Due to the use of include, if the file is not found, a warning is raised – even if another autoloader is capable of resolving the class later.
• Documenting how to setup the include_path has proven to be a difficult concept to convey.
• If multiple Zend Framework installations exist on the include_path, the first one on the path wins – even if that was not the one the developer intended.

To solve these problems, the StandardAutoloader by default requires that you explicitly register namespace/path pairs (or vendor prefix/path pairs), and will only load a file if it exists within the given path. Multiple pairs may be provided.

As a measure of last resort, you may also use the StandardAutoloader as a “fallback” autoloader – one that will look for classes of any namespace or vendor prefix on the include_path. This practice is not recommended, however, due to performance implications.

Finally, as with all autoloaders in Zend Framework, the StandardAutoloader is capable of registering itself with PHP’s SPL autoloader registry.

Note

Vocabulary: Namespaces vs. Vendor Prefixes

In terms of autloading, a “namespace” corresponds to PHP’s own definition of namespaces in PHP versions 5.3 and above.

A “vendor prefix” refers to the practice, popularized in PHP versions prior to 5.3, of providing a pseudo-namespace in the form of underscore-separated words in class names. As an example, the class Phly_Couch_Document uses a vendor prefix of “Phly”, and a component prefix of “Phly_Couch” – but it is a class sitting in the global namespace within PHP 5.3.

The StandardAutoloader is capable of loading either namespaced or vendor prefixed class names, but treats them separately when attempting to match them to an appropriate path.

Quick Start

Basic use of the StandardAutoloader requires simply registering namespace/path pairs. This can either be done at instantiation, or via explicit method calls after the object has been initialized. Calling register() will register the autoloader with the SPL autoloader registry.

If the option key ‘autoregister_zf’ is set to true then the class will register the “Zend” namespace to the directory above where its own classfile is located on the filesystem.

Manual Configuration

// This example assumes ZF is on your include_path.
// You could also load the autoloader class from a path relative to the
// current script, or via an absolute path.
require_once 'Zend/Loader/StandardAutoloader.php';
$loader = new Zend\Loader\StandardAutoloader(array('autoregister_zf' => true));

// Register the "Phly" namespace:
$loader->registerNamespace('Phly', APPLICATION_PATH . '/../library/Phly');

// Register the "Scapi" vendor prefix:
$loader->registerPrefix('Scapi', APPLICATION_PATH . '/../library/Scapi');

// Optionally, specify the autoloader as a "fallback" autoloader;
// this is not recommended.
$loader->setFallbackAutoloader(true);

// Register with spl_autoload:
$loader->register();

Configuration at Instantiation

The StandardAutoloader may also be configured at instantiation. Please note:

• The argument passed may be either an array or a Traversable object.
• The argument passed is also a valid argument for passing to the setOptions() method.

The following is equivalent to the previous example.

require_once 'Zend/Loader/StandardAutoloader.php';
$loader = new Zend\Loader\StandardAutoloader(array(
    'autoregister_zf' => true,
    'namespaces' => array(
        'Phly' => APPLICATION_PATH . '/../library/Phly',
    ),
    'prefixes' => array(
        'Scapi' => APPLICATION_PATH . '/../library/Scapi',
    ),
    'fallback_autoloader' => true,
));

// Register with spl_autoload:
$loader->register();

Configuration Options

The StandardAutoloader defines the following options.

StandardAutoloader Options

namespaces

An associative array of namespace/path pairs. The path should be an absolute path or path relative to the calling script, and contain only classes that live in that namespace (or its subnamespaces). By default, the “Zend” namespace is registered, pointing to the parent directory of the file defining the StandardAutoloader.

prefixes

An associative array of vendor prefix/path pairs. The path should be an absolute path or path relative to the calling script, and contain only classes that begin with the provided vendor prefix.

fallback_autoloader

A boolean value indicating whether or not this instance should act as a “fallback” autoloader (i.e., look for classes of any namespace or vendor prefix on the include_path). By default, false.

autoregister_zf

An boolean value indicating that the class should register the “Zend” namespace to the directory above where its own classfile is located on the filesystem.

Available Methods

__construct

Initialize a new instance of the object __construct($options = null)

Constructor Takes an optional $options argument. This argument may be an associative array or Traversable object. If not null, the argument is passed to setOptions().

setOptions

Set object state based on provided options. setOptions($options)

setOptions() Takes an argument of either an associative array or Traversable object. Recognized keys are detailed under Configuration options, with the following behaviors:

• The namespaces value will be passed to registerNamespaces().
• The prefixes value will be passed to registerPrefixes().
• The fallback_autoloader value will be passed to setFallbackAutoloader().

setFallbackAutoloader

Enable/disable fallback autoloader status setFallbackAutoloader($flag)

setFallbackAutoloader() Takes a boolean flag indicating whether or not to act as a fallback autoloader when registered with the SPL autoloader.

isFallbackAutoloader

Query fallback autoloader status isFallbackAutoloader()

isFallbackAutoloader() Indicates whether or not this instance is flagged as a fallback autoloader.

registerNamespace

Register a namespace with the autoloader registerNamespace($namespace, $directory)

registerNamespace() Register a namespace with the autoloader, pointing it to a specific directory on the filesystem for class resolution. For classes matching that initial namespace, the autoloader will then perform lookups within that directory.

registerNamespaces

Register multiple namespaces with the autoloader registerNamespaces($namespaces)

registerNamespaces() Accepts either an array or Traversable object. It will then iterate through the argument, and pass each item to registerNamespace().

registerPrefix

Register a vendor prefix with the autoloader. registerPrefix($prefix, $directory)

registerPrefix() Register a vendor prefix with the autoloader, pointing it to a specific directory on the filesystem for class resolution. For classes matching that initial vendor prefix, the autoloader will then perform lookups within that directory.

registerPrefixes

Register many vendor prefixes with the autoloader registerPrefixes($prefixes)

registerPrefixes() Accepts either an array or Traversable object. It will then iterate through the argument, and pass each item to registerPrefix().

autoload

Attempt to load a class. autoload($class)

autoload() Attempts to load the class specified. Returns a boolean false on failure, or a string indicating the class loaded on success.

register

Register with spl_autoload. register()

register() Registers the autoload() method of the current instance with spl_autoload_register().

Examples

Please review the examples in the quick start for usage.